Systems and methods for regenerating a spent catalyst

ABSTRACT

Systems and methods for regenerating a spent catalyst are provided. The method can include mixing a spent catalyst with a carrier fluid to provide a mixture. The spent catalyst can include carbon deposited on at least a portion thereof. The carrier fluid can include an oxygen containing gas. The mixture can be introduced to or above an upper surface of a dense phase catalyst zone disposed within a regenerator. A gas can be introduced to a lower zone of the dense phase catalyst zone. At least a portion of the carbon deposited on the catalyst can be combusted to provide a flue gas, heat, and a regenerated catalyst.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to systems andmethods for processing hydrocarbons. More particularly, embodiments ofthe present invention relate to systems and methods for regeneratingspent catalyst.

2. Description of the Related Art

Fluid catalytic crackers (“FCC”) are a mainstay in the conversion of rawhydrocarbons into one or more products. An FCC consists of fewcomponents: one or more riser reactors, one or more disengagers, and oneor more regenerators. A hydrocarbon feed and one or more catalysts areintroduced to the riser reactor which is maintained at an elevatedtemperature and/or pressure. The cracking of the hydrocarbons within theriser reactor produces one or more cracked hydrocarbons and smallquantities carbonaceous coke which is deposited on the surface of thecatalyst. The coke includes mostly carbon, but also contains hydrogen,sulfur, nitrogen, and trace amounts of other elements. These cokedeposits reduce the catalyst activity after passage through the riserreactor. The cracked hydrocarbons and the coked catalyst or (“spentcatalyst”) exit the riser reactor and are introduced to one or moredisengagers where the spent catalyst is separated from the crackedhydrocarbons. The cracked hydrocarbons are removed from the FCC forfurther processing and/or treatment. The spent catalyst is introduced toone or more regenerators where the coke is combusted, oxidized, and/orconverted to one or more waste gases.

The combustion process removes coke from the surface of the catalyst,regenerating the catalyst, and permitting its recycle back to the riserreactor. However, the combustion process generates undesirablebyproducts, such as nitrogen oxides (“NOx”), which must be removed or atleast partially reduced to meet environmental regulations.

There is a need, therefore, for improved systems and methods forregenerating catalyst while producing less undesirable byproducts.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the recited features of the present invention can be understoodin detail, a more particular description of the invention may be had byreference to embodiments, some of which are illustrated in the appendeddrawings. It is to be noted, however, that the appended drawingsillustrate only typical embodiments of this invention and are thereforenot to be considered limiting of its scope, for the invention may admitto other equally effective embodiments.

FIG. 1 depicts a partial cross-sectional view of an illustrativecatalyst regeneration system having a spent catalyst distributordisposed above a dense phase catalyst bed, according to one or moreembodiments described.

FIG. 2 depicts a partial cross-sectional view of an illustrativecatalyst regeneration system having a spent catalyst distributor andfluid introduction nozzles disposed above a dense phase catalyst bed,according to one or more embodiments described.

FIG. 3 depicts a partial cross-sectional view of the illustrativecatalyst regeneration system depicted in FIG. 1, further including anillustrative variable oxygen content carrier fluid generation system,according to one or more embodiments described.

FIG. 4 depicts a partial cross-sectional view of an illustrativecatalyst regeneration system having a spent catalyst introduction linein fluid communication with a dense phase catalyst bed and one or morefluid introduction nozzles disposed above the dense phase catalyst bed,according to one or more embodiments described.

FIG. 5 depicts a partial cross-sectional top view of an illustrativecatalyst regenerator, according to one or more embodiments described.

FIG. 6 depicts an illustrative fluid catalytic cracking system accordingto one or more embodiments described.

DETAILED DESCRIPTION

A detailed description will now be provided. Each of the appended claimsdefines a separate invention, which for infringement purposes isrecognized as including equivalents to the various elements orlimitations specified in the claims. Depending on the context, allreferences below to the “invention” may in some cases refer to certainspecific embodiments only. In other cases it will be recognized thatreferences to the “invention” will refer to subject matter recited inone or more, but not necessarily all, of the claims. Each of theinventions will now be described in greater detail below, includingspecific embodiments, versions and examples, but the inventions are notlimited to these embodiments, versions or examples, which are includedto enable a person having ordinary skill in the art to make and use theinventions, when the information in this patent is combined withpublicly available information and technology.

Systems and methods for regenerating a spent catalyst are provided. Themethod can include mixing a spent catalyst with a carrier fluid toprovide a mixture. The spent catalyst can include carbon deposited on atleast a portion thereof. The carrier fluid can include an oxygencontaining gas. The mixture can be introduced to or above an uppersurface of a dense phase catalyst zone disposed within a regenerator. Agas can be introduced to a lower zone of the dense phase catalyst zone.At least a portion of the carbon deposited on the catalyst can becombusted to provide a flue gas, heat, and a regenerated catalyst.

FIG. 1 depicts a partial cross-sectional view of an illustrativecatalyst regeneration system 100 having a spent catalyst distributor 150disposed above a dense phase catalyst bed 145, according to one or moreembodiments. The catalyst regeneration system 100 can include one ormore regenerators 140. The regenerator 140 can include the dense phasecatalyst zone 145, a dilute phase catalyst zone 155, one or moredistributors 150, one or more fluid introduction nozzles (two are shown160), and one or more cyclones (two are shown 165).

The dense phase catalyst zone 145 can be disposed toward a first end 141of the regenerator 140 and the dilute phase catalyst zone 155 can bedisposed toward a second end 142 of the regenerator 140. The dilutephase catalyst zone 155 can have a spent catalyst and/or regeneratedcatalyst concentration ranging from a low of about 0 kg/m³, about 50kg/m³, or about 100 kg/m³ to a high of about 140 kg/m³, about 160 kg/m³,about 175 kg/m³, or more. The dense phase catalyst zone 145 can have aspent catalyst and/or regenerated catalyst concentration ranging from alow of about 240 kg/m³, about 320 kg/m³, about 375 kg/m³ to a high ofabout 420 kg/m³, about 475 kg/m³, about 525 kg/m³, or more.

The dense phase catalyst zone 145 can be referred to as having a firstor “lower” zone 146, a second or “middle” zone 147, and a third or“upper” zone 148. The regenerator 140, as shown in FIG. 1 and discussedand described herein, is with reference to a vertical, cylindrical,regenerator 140 with the dense phase catalyst zone 145 disposed belowthe dilute phase catalyst zone 155 and an L/D ratio of greater than 1,however, any orientation or configuration can be used.

The first zone 146 can include the lower portion or region of the densephase catalyst zone 145. The third zone 148 can include the upperportion or region of the dense phase catalyst zone 145. The third zone148 can also be referred to as a “transitional zone” that can span aregion intermediate the dense phase catalyst zone 145 and the dilutephase catalyst zone 155. The transitional zone 148 can have a fluid beddensity intermediate the density of the lower density dilute phasecatalyst zone 155 and the higher density first and second catalyst zones146, 147, respectively. The second zone 147 can include the middleportion or region disposed between the first zone 146 and the third zone148.

In one or more embodiments, the one or more distributors 150 can bedisposed within the transitional zone 148 between the surface 149 of thedense phase catalyst zone 145 and the second end 142 of the regenerator140. The distributor 150 can include one or more ports or nozzles 152 toprovide fluid communication from line 135, through the distributor 150and to the regenerator 140. In at least one specific embodiment, thedistributor 150 or at least the nozzles 152 can be disposed within thedense phase catalyst bed 145. For example, the distributor 150 or atleast the nozzles 152 can be disposed within the third zone 148 of thedense phase catalyst zone 145. In another example, the distributor 150or at least the nozzles 152 can be disposed within the second or middlezone 147.

In one or more embodiments, the fluid introduction nozzles 160 can bedisposed within the dense phase catalyst zone 145 toward the first end141 of the regenerator 140. For example, the fluid introduction nozzles160 can be disposed within the first zone 146 of the dense phasecatalyst zone 145.

A carrier fluid via line 130 and spent catalyst via line 131 can beintroduced to line 135 to provide a mixture of spent catalyst andcarrier fluid. The spent catalyst can include carbon or coke at leastpartially disposed thereon and/or therein. The mixture of spent catalystand carrier fluid via line 135 can be introduced to the distributor 150,which can introduce the mixture to the regenerator 140 via the one ormore exit ports or nozzles 152. In one or more embodiments, thedistributor 150 can distribute the mixture about the surface 149 of thedense phase catalyst zone 145. In one or more embodiments, thedistributor 150 can distribute the mixture above the surface 149 of thedense phase catalyst zone 145. For example, the mixture can beintroduced to the dilute phase catalyst zone 155. In one or moreembodiments, the distributor 150 can distribute the mixture beneath thesurface 149 of the dense phase catalyst zone 145 and within the thirdzone 148 of the dense phase catalyst zone 145. In one or moreembodiments, the distributor 150 can distribute a portion of the mixtureabove the surface 149 and a portion below the surface 149 of the densephase catalyst zone 145. In one or more embodiments, the distributor 150can distribute the mixture to the second or middle zone 147, the thirdor upper zone 148, the dilute phase catalyst zone 155, or anycombination thereof.

The carrier fluid via line 130 can be or include any suitable fluid.Illustrative carrier fluids can include, but are not limited to, air,oxygen-lean gas, oxygen-rich gas, ozone, steam, carbon monoxide (“CO”),carbon dioxide (“CO₂”), combustion or exhaust gas, or any combinationthereof. As used herein, the term “oxygen-lean” refers to a gascontaining less oxygen than air. As used herein, the term “oxygen-rich”refers to a gas containing more oxygen than air.

A fluid or gas via line 119 can be introduced to the fluid introductionnozzles 160. The fluid can provide sufficient velocity or motive forcewithin the dense phase catalyst zone 145 to provide a fluidized catalystzone. In other words, the dense phase catalyst zone 145 can be afluidized catalyst zone. The fluid introduced via nozzles 160 can flowthrough the dense phase catalyst zone 145 toward the second end 142 ofthe regenerator 140.

The fluid introduced via nozzles 160 can be any suitable fluid ormixture of fluids. For example, the fluid introduced via line 119 to theregenerator 140 can include, but is not limited to, air, oxygen-richgas, oxygen-lean gas, ozone, CO, CO₂, nitrogen, steam, combustion orexhaust gas, or any combination thereof.

When the fluid introduced via nozzles 160 includes an oxidant, the fluidcan flow through the dense phase zone 145 and the oxidant present cancombust or otherwise burn at least a portion of the carbon or cokedeposited on the spent catalyst and/or coke dust to provide aregenerated catalyst via line 177 and a combustion gas or flue gas vialine 170. The regeneration, i.e. combustion of the coke deposited onand/or within the catalyst can re-expose the reactive surfaces of thecatalyst, thereby regenerating the catalyst and permitting reuse. Theflue gas can contain oxygen, CO, CO₂, NOx, and/or sulfur oxides (“SOx”)among other components. The CO produced during combustion of the spentcatalyst can be further oxidized with the oxidant present therein toform CO₂.

The amount of oxygen introduced via the carrier fluid in line 130 canrange from a low of about 0.5%, about 1%, about 3%, about 5%, or about10% to a high of about 50%, about 55%, or about 60% of the total amountof oxygen introduced to the regenerator 140 via lines 130 and 119. Inanother example, the amount of oxygen introduced via the carrier fluidin line 130 can be about 15%, about 20%, or about 25% of the totalamount of oxygen introduced via lines 130 and 119 to the regenerator140. The amount of oxygen introduced via the fluid in line 119 can rangefrom a low of about 40%, about 45%, or about 50% to a high of about 75%,about 85%, about 95%, or about 99.5% of the total amount of oxygenintroduced to the regenerator 140 via line 130 and/or line 119. Forexample, the amount of oxygen introduced via line 119 can be about 75%,about 80%, or about 85% of the total amount of oxygen introduced vialines 130 and 119. The amount of oxygen introduced to the regenerator140 via lines 119 and 130 can remain constant or can vary. The amount ofoxygen introduced to the regenerator 140 via lines 119 and 130 canremain constant or can vary with respect to one another.

The cyclones 165 can separate at least a portion of any entrainedcatalyst and/or other particulates, such as non-combusted cokeparticles, in the flue gas to provide a solids-lean flue gas via line166 and separated catalyst and other particulate matter via line 167.The cyclones 165 can provide catalyst separation efficiency greater thanabout 90%, about 95%, about 98%, about 99%, about 99.5%, about 99.9%, orabout 99.99%. The separated catalyst and/or other particulates can bereintroduced to the dense phase catalyst zone 145 via lines 167. Thesolids-lean flue gas via line 166 can be introduced to plenum 168. Thesolids-lean flue gas via lines 166 from multiple cyclones 165 can bemixed within the plenum 168 and recovered as a flue gas via line 170from the plenum 168.

In one or more embodiments, CO and/or coke afterburning can occur withinthe dilute phase catalyst zone 155, the cyclones 165, the plenum 168,and/or the flue gas recovery line 170. Afterburning of the CO and/orcoke can increase the temperature of the flue gas recovered via line170. For example, flue gas can enter the cyclones 165 at a temperatureof about 670° C. to about to about 695° C. and due to afterburning of COwithin the cyclones the flue gas exiting the cyclones 165 can be at atemperature of about 720° C. to about 765° C. However, the heatgenerated by the exothermic oxidation of the CO and/or coke can beacceptable, such that the flue gas temperature remains within catalystregeneration system 100 operational limits. For example, the temperatureof the flue gas with CO and/or coke afterburning can remain below about900° C., below about 850° C., below about 800° C., below about 775° C.,below about 760° C., or less.

The coke deposited on the spent catalyst introduced via nozzles 152and/or CO produced during combustion of the coke can reduce theformation of NOx within the regenerator 140. For example, the cokedeposited on the spent catalyst can reduce the formation of NOx withinthe dilute phase catalyst zone 155, thereby reducing the amount of NOxwithin the flue gas in line 170. Two potential or possible reactionpathways involving the carbon contained in coke on the spent catalystand CO generated during combustion can include:2NO+C→N₂+CO₂; and  (1)2NO+2CO→N₂+2CO₂  (2)

The above potential or possible reactions, among others, can provide aflue gas having reduced NOx concentrations, which can be due, at leastin part, to the increased amount of CO and/or carbon in the dilute phasecatalyst zone 155. In one or more embodiments, the NOx concentration inthe flue gas via line 170 can be less than about 150 ppm, less thanabout 100 ppm, less than about 75 ppm, less than about 50 ppm, less thanabout 40 ppm, less than about 30 ppm, less than about 20 ppm, about 15ppm, or less. For example, the NOx concentration in the flue gas canrange from about 15 ppm to about 45 ppm, about 15 ppm to about 27 ppm,about 25 ppm to about 40 ppm, or about 30 ppm to about 45 ppm.

The amount of oxidant via line 119 and/or in the carrier fluid via line130 can range from a low of about 80%, about 85%, or about 90% to a highof about 105%, about 110%, about 115%, or more of the stoichiometricoxygen required to oxidize the total amount of carbon and/or COintroduced and/or produced within the regenerator 140. In one or moreembodiments, 100% of the stoichiometric oxygen required for completecombustion and oxidation of the materials introduced to the regenerator140 can be introduced via line 119 and/or line 130. Excess oxygenranging from a low of about 0.1%, about 0.5%, or about 1% to a high ofabout 1.5%, about 2.5%, or about 3.5% more than the stoichiometricoxygen required to oxidize the total amount of carbon and/or COintroduced and/or produced within the regenerator 140 can be introducedvia line 119 and/or line 130. Introducing excess oxygen to theregenerator 140 can provide a flue gas via line 170 that contains oxygenranging from a low of about 0.1% mol, about 0.5% mol, or about 1% mol toa high of about 2% mol, about 3% mol, about 4% mol, or more. In at leastone specific embodiment the oxygen content of the flue gas via line 170can range from about 1.5% mol to about 2.5% mol.

The catalyst or catalyst particles can provide a heat sink within theregenerator 140. In other words, the catalyst particles can provideenough heat absorption to reduce the temperature within the regenerator140 due to the combustion of coke and/or CO. The catalyst particles canprovide enough heat absorption to prevent the temperature within theregenerator 140 from exceeding operational limits.

In one or more embodiments, the catalyst can include, but is not limitedto, one or more zeolites, metal impregnated catalysts, faujasitezeolites, modified faujasite zeolites, Y-type zeolites, ultrastableY-type zeolites (USY), rare earth exchanged Y-type zeolites (REY), rareearth exchanged ultrastable Y-type zeolites (REUSY), rare earth freeZ-21, Socony Mobil #5 zeolite (ZSM-5), ZSM-11, ZSM-12, ZSM-23, ZSM-35,ZSM-38, or any other high activity zeolite catalysts.

FIG. 2 depicts a partial cross-sectional view of an illustrativecatalyst regeneration system 200 having a spent catalyst distributor 150and fluid introduction nozzles 205 disposed above a dense phase catalystbed 145, according to one or more embodiments. The catalyst regenerationsystem 200 can be similar to the catalyst regeneration system 100discussed and described above with reference to FIG. 1, and can furtherinclude one or more fluid introduction nozzles 205 disposed above thedense phase catalyst bed 145 within the regenerator 140. The catalystregeneration system 200 can also include one or more CO promoterintroduction lines 215 in fluid communication with the spent catalyst inline 131. The nozzles 205 can be disposed above the surface 149 of thedense phase catalyst bed 145. In one or more embodiments, a fluid vialines 203 can be introduced to one or more nozzles 205. The fluidintroduced via line 203 can include, but is not limited to, air,oxygen-rich gas, oxygen-lean gas, ozone, CO, CO₂, nitrogen, steam,combustion or exhaust gas, or any combination thereof. In one or moreembodiments, a fluid introduced via line 203 that includes an oxidantcan further oxidize CO and/or coke therein. The amount of oxygenintroduced via the fluid in line 203 can range from a low of about 0.5%,about 1%, about 3%, or about 5% to a high of about 20%, about 30%, about40%, or about 50% of the total amount of oxygen introduced to theregenerator 140 via lines 130, 119, and 203. The amount of oxygenintroduced via the carrier fluid in line 130 can range from a low ofabout 0.5%, about 1%, about 3%, or about 5% to a high of about 20%,about 30%, about 40%, or about 50% of the total amount of oxygenintroduced to the regenerator 140 via lines 130, 119, and 203. Theamount of oxygen introduced with the fluid via line 119 can range from alow of about 40%, about 45%, or about 50% to a high of about 75%, about85%, or about 95% of the total amount of oxygen introduced to theregenerator 140 via lines 130, 119, and 203. The amount of oxygenintroduced via the carrier fluid in line 130 and the fluid via line 203can range from a low of about 0.5%, about 1%, about 3%, or about 5% to ahigh of about 20%, about 40%, about 60%, or about 70% of the totalamount of oxygen introduced to the regenerator 140 via lines 130, 119,and 203. For example, the amount of oxygen introduced via lines 130 and203 can be about 15%, about 20%, about 25%, about 30%, or about 35% ofthe total amount of oxygen introduced to the regenerator via lines 130,119, and 203.

The one or more CO oxidation promoters via line 215 can be introduceddirectly to the mixture in line 135, the carrier fluid in line 130,and/or the spent catalyst in line 131. The CO oxidation promoter canreduce the temperature at which CO combusts within the regenerator 140,thereby converting CO to CO₂ at a lower temperature to provide a fluegas via line 170 containing little or no CO. For example, the COconcentration in the flue gas via line 170 can be less than about 2%mol, less than about 1.5% mol, less than about 1% mol. less than about0.7% mol, less than about 0.5% mol, less than about 0.3% mol, less thanabout 0.1% mol, or less than about 0.01% mol.

The CO oxidation promoter can include, but is not limited to, platinum,palladium, iridium, rhodium, osmium, ruthenium, and rhenium, oxidesthereof, derivatives therefore, or any combination thereof. In one ormore embodiments, the CO oxidation promoter can be disposed on asupport. Suitable supports can include, but are not limited to, silica,alumina, and silica-alumina. Examples of commercially available aluminasupports are available under trade names such as PURALOX, CATAPAL andVERSAL. Examples of commercially available silica-alumina supports areavailable under trade names such as SIRAL and SIRALOX.

The CO oxidation promoter can be categorized based upon the amount ofthe CO oxidation promoter present within the regeneration system 200.For example, a low activity level CO oxidation promoter can be referredto as having a concentration of the active ingredient, e.g. platinum,within the regeneration system 200 ranging from greater than zero to ahigh of about 0.3 ppm. A medium activity level CO promoter can bereferred to as having a concentration of the active ingredient, e.g.platinum, within the regeneration system 200 ranging from about 0.3 ppmto about 0.9 ppm. A high activity level CO promoter can be referred toas having a concentration of the active ingredient, e.g. platinum,within the regeneration system 200 ranging from a low of about 0.9 ppmto a high of about 2 ppm. A high activity level CO promoter can bepresent at a concentration greater than 2 ppm, for example about 2.5ppm, about 3 ppm, or about 4 ppm.

The presence of a CO oxidation promoter can reduce the temperature atwhich CO will burn, which can reduce the temperature of the flue gas asmore of the CO will burn in the dense phase catalyst zone 145 ratherthan in the dilute phase catalyst zone 155. The reduction in the COcombustion temperature can prevent or reduce a temperature rise withinthe regenerator 140 and in particular the dilute phase catalyst zone 155from exceeding operationally safe limits. The temperature within theregenerator 140 and in particular the dilute phase catalyst zone 155 canbe maintained below about 900° C., below about 850° C., below about 800°C., below about 775° C., below about 760° C., or less.

In one or more embodiments, the presence of a CO oxidation promoter canpromote the combustion of CO within the dense phase catalyst bed 145.The combustion of at least a portion of the CO within the dense phasecatalyst bed 145 can reduce the amount of CO combusted within the dilutephase catalyst bed 155, where a higher temperature is more likely orprobable, due to the presence of less catalyst particles and therefore,less heat sink.

In one or more embodiments, fresh or “make-up” catalyst can be added vialine 210 to the regenerator 140. The make-up catalyst can be introducedto maintain a predetermined amount of catalyst within the catalystregeneration system 200. The introduction of make-up catalyst via line210 can be introduced to the spent catalyst in line 131, the spentcatalyst mixture in line 135, the regenerator 140, the regeneratedcatalyst in line 177 or any other suitable location within the catalystregeneration system 200.

FIG. 3 depicts a partial cross-sectional view of the illustrativecatalyst regeneration system 100 depicted in FIG. 1, further includingan illustrative variable oxygen content carrier fluid generation system300, according to one or more embodiments. The variable oxygen contentcarrier fluid generation system (“carrier fluid system”) 300 caninclude, but is not limited to, one or more turbines 105, one or moreblowers 115, and one or more heaters 125.

The turbine 105 can provide a combustion gas or exhaust gas via line109. In one or more embodiments, the blower can provide compressed vialine 117. The gas introduced to the blower 115 via line 111 can include,but is not limited to, air, oxygen-rich gas, oxygen-lean gas, CO, CO₂,or any combination thereof. In one or more embodiments, the combinationof the turbine 105, blower 115, and/or heater 125 can be operated toprovide a carrier gas via line 130 ranging from an oxygen-lean gas to anoxygen-rich gas via line 130 having a predetermined temperature,pressure, and velocity. The turbine 105, blower 115, and/or heater 125can be replaced with any system suitable for providing a carrier gas vialine 109 ranging from an oxygen-lean gas to an oxygen-rich gas. In oneor more embodiments, steam via line 129 can be introduced to thecombustion gas 109, the compressed gas in line 127, or a mixture thereofto provide a carrier gas via line 130 that includes steam. In oneexample, steam via line 129 can be introduced as the carrier fluid vialine 130. As illustrated, the fluid in line 119 can be provided by theblower 115. Although not shown, the fluid in line 119 can be pre-heatedprior to introduction to the regenerator 140 via the nozzles 160.

The turbine 105 can be any turbine suitable for generating power. Forexample, the turbine 105 can be a gas turbine in which a fuel and anoxidant can be combusted in a combustor and compressed upstream of theturbine. The compressed combusted gas can then be introduced to the gasturbine to generate power in one or more generators (not shown) and toprovide a hot gas or exhaust gas via line 107. Another suitable type ofturbine can be a combustion turbine where the combustion of the fuel canbe integrated within the turbine (i.e. the combustion of the fuel occurswithin the turbine). The fuel can be any suitable fuel, such as syngas,hydrogen, methane, other combustible fuel, or mixtures thereof. In oneor more embodiments, a fuel via line 102 and an oxidant via line 104 canbe introduced to the turbine 105 which can be combusted to provide theexhaust gas via line 107 and power to drive the blower 115.

The blower 115 can be any blower suitable for providing a compressed gasvia line 117. In at least one specific embodiment, the blower 115 can beindependently driven, i.e. the blower can be powered by equipment otherthan the turbine 105.

The heater 125 can include any system, device, or combination of systemsand/or devices suitable for heating a fluid. In one or more embodiments,the fluid via line 117 can be indirectly heated within the heater 125.In one or more embodiments, the fluid via line 117 can be directlyheated within the heater 125, for example by mixing with the combustionproducts provided by the combustion of a fuel introduced via line 121.

In one or more embodiments, other equipment that can be used to providea variable oxygen content carrier fluid can include, but is not limitedto, one or more air separation units, which can provide an oxygen-richgas, other combustion systems, or the like. The air separation unit caninclude cryogenic distillation, pressure swing adsorption, membraneseparation, or any combination thereof.

FIG. 4 depicts a partial cross-sectional view of an illustrativecatalyst regeneration system 400 having a spent catalyst introductionline in 305 fluid communication with a dense phase catalyst bed 145 andone or more fluid introduction nozzles 405 disposed above the densephase catalyst bed 145, according to one or more embodiments. Referringto both FIGS. 3 and 4, the catalyst regeneration systems 300, 400 caninclude one or more regenerators 140, one or more turbines 105, one ormore blowers 115, and/or one or more heaters 125, which can be the sameas those discussed and described above with reference to FIG. 1. Similaras discussed and described above with reference to FIG. 1, theregenerator 140 can include a dense phase catalyst zone 145, a dilutephase catalyst zone 155, one or more fluid introduction nozzles (two areshown 160), one or more cyclones (two are shown 165), one or moreplenums 167, one or more flue gas recovery lines 170, and one or moreregenerated catalyst recovery outlets 175. The catalyst regenerationsystem 400 can further include one or more nozzles 405 disposed abovethe surface 149 of the dense phase catalyst bed 145.

A carrier fluid via line 130 and spent catalyst via line 131 can beintroduced to line 305 to provide a mixture of spent catalyst andcarrier fluid. In one or more embodiments, line 305 can be in fluidcommunication with the dense phase catalyst zone 145. In one or moreembodiments, the spent catalyst and carrier fluid via line 305 can beintroduced to the first zone 146 of the dense phase catalyst zone 145.In one or more embodiments, the spent catalyst and carrier fluid vialine 305 can be introduced to the second zone 147 of the dense phasecatalyst zone 145. In one or more embodiments, the spent catalyst andcarrier fluid via line 305 can be introduced to the third zone 148 ofthe dense phase catalyst zone 145. In one or more embodiments, the spentcatalyst and carrier fluid via line 305 can be introduced to the firstzone 146, the second zone 147, the third zone 148, or any combinationthereof. The carrier fluid introduced via line 130 can be any suitablecarrier fluid. Similar as discussed and described above with referenceto FIG. 1, the carrier fluid in line 130 can include a gas ranging fromoxygen-lean to oxygen-rich.

A gas or fluid containing an oxidant, e.g. oxygen gas, introduced vialine 119 to the nozzles 160, an oxidant present in the carrier gasintroduced via line 130, and/or an oxidant introduced via the nozzles405 can combust or oxidize the coke deposited on the catalyst introducedvia line 131 to provide a flue gas via line 170 and a regeneratedcatalyst via line 177, as discussed and described above with referenceto FIGS. 1-3. The fluid introduced via line 119 to the nozzles 160 canintroduce enough fluid velocity within the dense phase catalyst bed 145to provide a fluidized catalyst bed 145.

A fluid via line 403 can be introduced to the one or more nozzles 405disposed within the regenerator 140 of the catalyst regeneration system400. Illustrative fluids can include, but are not limited to, air,oxygen-rich gas, oxygen-lean gas, ozone, steam, CO, CO₂, nitrogen,exhaust or combustion gas, or any combination thereof. The catalystregeneration system 400 can also include a CO oxidation promoterintroduction line 215 and/or make-up catalyst introduction line 210, asdiscussed and described above with reference to FIG. 2.

The amount of oxygen introduced via the fluid in line 403 can range froma low of about 3%, about 5%, about 7%, or about 9% to a high of about20%, about 30%, about 40%, or about 50% of the total amount of oxygenintroduced to the regenerator 140 via lines 130, 119, and 403.

FIG. 5 depicts a partial cross-sectional top view of an illustrativecatalyst regenerator 140, according to one or more embodiments. FIG. 5illustrates one exemplary configuration of the cyclones 165 and fluidintroduction nozzles 160 disposed within the regenerator 140. Asillustrated in FIG. 5, the distributor 150, lines 135, 210, or 305, andthe fluid introduction nozzles 205, which are shown in FIGS. 1, 2, 3,and/or 4, are left out for clarity.

A plurality of fluid introduction nozzles 160 can be distributed about alower portion of the regenerator 140. As shown, nine fluid introductionnozzles 160 are shown distributed about the regenerator 140. Also shown,are four cyclones 165 disposed within the regenerator 140. Any number offluid introduction nozzles 160 and any number of cyclones 165 can bedisposed within the regenerator 140. The number and particular placementof the fluid introduction nozzles 160 and cyclone 165 can be determined,at least in part, based on the particular catalyst regeneration system100, 200, 300, and 400 operational requirements.

The flue gas and entrained particulates, such as catalyst particles, canenter the cyclones via cyclone inlet 505. The cyclones can then separatesolids or particulates from the flue gas to provide a solids-lean fluegas. The solids-lean flue gas can be recovered via line 170 and theparticulates can be returned to the dense phase catalyst zone 145, asdiscussed and described above with reference to FIGS. 1-4.

FIG. 6 depicts an illustrative fluid catalytic cracking system 600,according to one or more embodiments. The FCC system 600 can include afluidized catalytic cracker (“FCC”) 603 or any other suitable systemhaving one or more risers 605, ducts 610, separation zones 615, andregenerators 140. The regenerator 140 can be similar to the regenerators140 discussed and described above with reference to FIGS. 1-5. In one ormore embodiments, the system 600 can further include a gas turbine 105,a blower 115, and an air heaters 125, which can be similar as discussedand described above with reference to FIGS. 1-4. In one or moreembodiments, steam via line 630, one or more hydrocarbons via line 635,and one or more catalysts via line 177 can be introduced to the one ormore risers 605, forming a fluidized mixture (“reaction mixture”)therein. The steam via line 630 and the catalyst via line 177 can be fedseparately to the riser 605 as shown in FIG. 6, or the steam and thecatalyst can be mixed and fed together as a mixture to the riser 605.

Heat in the riser 605 provided by the steam via line 630 and thecatalyst via line 170 can vaporize the hydrocarbon feed via line 635entering the riser via line 605, to provide the reaction mixturetherein. Supplemental heat and/or firing can be provided to the one ormore risers 605 using waste heat (not shown) provided from theregenerator 140. Within the riser 605, the hydrocarbons within thereaction mixture can be cracked into one or more hydrocarbons andhydrocarbon by-products to provide a first product mixture. At least aportion of the hydrocarbon by-products present in the riser 605 candeposit on the surface of the catalyst particles, forming coked-catalystparticles or spent catalyst. Thus, the first product mixture exiting theriser 605 can contain coked-catalyst particles suspended in gaseoushydrocarbons, hydrocarbon by-products, coke dust or particulates, steam,and other inerts.

The amount of coke or carbon deposited on the catalyst particles canrange from about 0.01% wt to about 5% wt, about 0.1% wt to about 4% wt,or about 0.15% wt to about 3% wt. For example, the amount of coke orcarbon deposited on the catalyst particles can range from a low of about0.01% wt, about 0.1% wt, or about 0.5% wt to a high of about 1% wt,about 1.2% wt, or about 1.4% wt. In another example, the amount of cokedeposited on the catalyst particles can range from about 0.5% wt toabout 1.5% wt, from about 0.7% wt to about 1.1% wt, or from about 0.9%wt to about 1.2% wt. In at least one specific embodiment, the amount ofcoke deposited on the catalyst particles can be about 1% wt.

In one or more embodiments, the catalyst-to-hydrocarbon weight ratio canrange from about 4:1 to about 8:1; from about 4.5:1 to about 7.5:1; orfrom about 5:1 to about 7:1. In one or more embodiments, the riser 605can be operated at a temperature ranging from a low of about 475° C.,about 490° C., or about 500° C. to a high of about 550° C., about 600°C., or about 650° C. For example, the riser 605 can be operated at atemperature ranging from about 500° C. to about 595° C., from about 505°C. to about 585° C., or from about 510° C. to about 565° C.

The velocity of the reaction mixture flowing through the riser 605 canrange from about 3 m/sec to about 27 m/sec, about 6 m/sec to about 25m/sec, or about 9 m/sec to about 21 m/sec. The residence time of thereaction mixture in the riser 605 can be less than about 20 seconds,less than about 10 seconds, less than about 8 seconds, less than about 4seconds, or less than about 2 seconds.

The first product mixture can flow, via the duct (or transition line)610, to the one or more separation zones 615 where the coked-catalystparticles and/or other particulates can be separated from the gaseoushydrocarbons, steam, and inerts. The separation zone 615 can have alarger cross-sectional area than either the riser 605 or the duct 610 toreduce the velocity of the gas, allowing the heavier coked-catalystparticles and/or other particulates to separate from the gaseoushydrocarbons, steam, and inerts. In one or more embodiments, a steampurge (not shown) can be added the separation zone 615 to assist inseparating the gaseous hydrocarbons from the coked-catalyst particles,i.e. stripping the gaseous hydrocarbons from the solids.

The gaseous hydrocarbons (“first product”) via line 650 can be recoveredfrom the separation zone 615. Although not shown, in one or moreembodiments, the first product in line 650 can be further processed,such as by dehydrating or fractionating to provide one or more finishedproducts including, but not limited to, one or more olefins, paraffins,aromatics, mixtures thereof, derivatives thereof, and/or combinationsthereof. The solids, i.e. coked-catalyst particles, can free fallthrough the separation zone discharge 131 toward the regenerator 140.

Within the regenerator 140, the coked-catalyst particles and carrierfluid mixture via line 135 can be combined with the fluid introduced vialine 119 to provide the flue gas via line 170 and regenerated catalystvia line 177, as discussed and described above with reference to FIGS.1-5.

The flue gas in line 170 can be introduced to one or more optional COboilers (not shown) to remove additional CO. The one or more CO boilerscan be any type of CO boiler, which are well-known. The CO boiler can beoperated in multiple stages to reduce the flame temperature occurring inany one stage and limit NOx formation in an oxidizing atmosphere. LowNOx burners can also be used to burn the fuel gas (not shown) which maybe needed to keep the CO boiler lit.

The cleaned flue gas via line 170 introduced to one or more optional COboilers can contain very little that will burn. Most or all of the NOxand NOx precursors in the flue gas can be eliminated within theregenerator 140 where most or all the CO in the flue gas can beeliminated as well. The flue gas in line 170 can have a heating value ofless than about 7,500 kJ/m³, less than about 3,700 kJ/m³, less thanabout 2,800 kJ/m³, less than about 1,900 kJ/m³, less than about 950kJ/m³, or less than about 400 kJ/m³.

In one or more embodiments, ammonia or an ammonia precursor such as ureacan be introduced (not shown) to the optional CO boiler (not shown) toreduce NOx emissions even further. These materials can react quicklywith NOx and NOx precursors to reduce it to nitrogen. Additional detailsfor conventional FCC processes and flue gas treatment can be found inU.S. Pat. Nos. 5,268,089; 4,514,285; and 5,773,378; which areincorporated by reference herein.

In one or more embodiments, at least a portion of the flue gas via line170 and/or flue gas from the one or more optional CO boilers can bevented to the atmosphere and/or sent to a heat recovery unit (not shown)and then vented to the atmosphere, sequestered under ground, orotherwise disposed. The one or more optional CO boilers, if used canreduce the CO content of the flue gas in line 170 by about 50%, about70%, about 80%, about 90%, about 95%, about 98%, about 99%, about 99.5%,about 99.9%, or about 99.99%. In one or more embodiments, the one ormore optional CO boilers can reduce the CO content of the flue gas inline 170 by from about 50% to about 99%; from about 95% to about 99.99%;from about 97% to about 99.9%; or from about 99% to about 99.99%.

Although not shown, in one or more embodiments, a carbon dioxide (CO₂)separation unit can be used to remove at least a portion of the CO₂ fromthe flue gas in line 170. In one or more embodiments, CO₂ can be removedfor sequestration or reuse, e.g., reuse through enhanced oil recovery.

In one or more embodiments, the one or more optional heat recovery units(not shown) can include any device, system or combination of systemsand/or devices suitable for transferring heat from a fluid at a highertemperature to a fluid at a lower temperature. In one or moreembodiments, the heat recovery unit can include, but is not limited tosingle or multiple pass heat exchange devices such as shell and tubeheat exchangers, plate and frame heat exchangers, spiral heatexchangers, bayonet type heat exchangers, U-tube heat exchangers, and/orany similar system or device.

Within the regenerator 140 a fluidized mixture, containing spentcatalyst particles, regenerated catalyst particles, oxidants, carbonmonoxide, carbon dioxide, nitrogen oxides, and/or the one or more fluidsintroduced via line 119 can be combined within the regenerator 140 withone or more optional doping agents introduced via line 675. Thedispersal and deposition of the one or more doping agents on theregenerated catalyst can be enhanced by the high temperature and/orturbulence present in the regenerator 140.

Supplemental fuel, for example natural gas, can be introduced to theregenerator 140 via line 675. The use of supplemental fuel can provideadditional heat within the regenerator 140, further enhancing theregeneration of the coked-catalyst particles therein.

Turbulence within the regenerator 140 can improve the even dispersion ofthe one or more doping agents within the fluidized catalyst zone 145,increasing the contact between the one or more doping agents with thereactive surfaces on the regenerated catalyst. In contrast, the one ormore doping agents in a traditional, homogeneously doped, catalyst aredispersed within the catalyst particles. Consequently, less doping agentcan be used to achieve the same concentration of doping agent on thesurface of the regenerated catalyst particle. Also, changing dopingagents in response to changing process conditions and/or hydrocarbonfeed composition can be more readily achieved since little or noentrained doping agent exists within the catalyst particle, i.e. theinterior matrix of the catalyst particle. For example, the doping agentcan be changed simply by changing the type and/or composition of thedoping agent added to the regenerator 140.

The selection of an appropriate doping agent or additive or blend of twoor more doping agents or additives can be based upon the composition ofthe incoming hydrocarbon feed via line 635, and/or desired gaseoushydrocarbons in the first product exiting the separation zone 615 vialine 650. For example, the addition of a class 2 doping agent such asmagnesium or barium can preferentially increase the production ofethylene in the first product in line 650. The addition of a class 13doping agent such as gallium can result in the increased production ofaromatic hydrocarbons in the first product in line 650. The addition ofclass 8, 9, or 10 doping agents such as ruthenium, rhodium or palladiumcan preferentially increase the production of propylene in the firstproduct in line 650.

Doped catalyst particles and/or regenerated catalyst particles with orwithout one or more doping agents or additives can be recycled to theone or more risers 605 via line 177. In one or more embodiments, theflow of regenerated catalyst from the regenerator 140 can be controlledusing one or more valves (not shown), which can be manually orautomatically adjusted or controlled based upon parameters derived fromprocess temperatures, pressures, flows and/or other process conditions.In one or more embodiments, at least 90% wt, at least 95% wt, at least99% wt, at least 99.99% wt, at least 99.9975% wt, or at least 99.999% wtof the total catalyst and/or doped catalyst originally introduced to theriser 605 via line 177 can be regenerated, optionally doped with one ormore doping agents, and recycled back to the riser 605.

The hydrocarbon feed in line 635 can include any suitable hydrocarbon ormixture of hydrocarbons. For example, the hydrocarbon feed in line 635can include, but is not limited to, naphtha, gas oils, deasphalted oils,recycle gas oils, coker gas oils, vacuum gas oils, vacuum residua,Atmospheric residua. The hydrocarbon feed in line 635 can include anycombination of C₂ to C₄₀₊ hydrocarbons. For example, the hydrocarbonfeed in line 635 can include C₅ to C₁₁, C₁₁ to C₁₉, C₁₆ to C₂₅, C₁₆ toC₄₀, C₂₀ to C₄₀, C₄₀ to C₁₀₀ hydrocarbons or any combination or mixturethereof. The hydrocarbon feed in line 635 can include, but is notlimited to, olefins, paraffins, naphthenes, and/or mixtures thereof. Inone or more embodiments, the hydrocarbon feed can originate from arefinery. For example, the hydrocarbon feed can be a gas mixtureresulting from the distillation of crude oil. In one or moreembodiments, the hydrocarbon feed in line 635 can include at least 60%wt C₂-C₁₁ olefins and paraffins.

The hydrocarbon feed introduced via line 635 can be pre-heated (notshown) prior to introduction to the riser 605. Although not shown inFIG. 6, a regenerative heat exchanger using waste process heat can beused to pre-heat the hydrocarbon feed. The temperature of thehydrocarbon feed can range from about 175° C. to about 375° C., about225° C. to about 350° C., or about 250° C. to about 325° C. The pressureof the hydrocarbon feed can range from about 100 kPa to about 3,450 kPa,about 100 kPa to about 2,750 kPa, or about 100 kPa to about 350 kPa.

The hydrocarbon feed introduced via line 635 can be partially orcompletely vaporized prior to introduction to the one or more risers605. The hydrocarbon feed can be about 10% vol to about 100% vol; about20% vol to about 60% vol; about 30% vol to about 60% vol; about 40% volto about 60% vol; or about 50% vol to about 60% vol vaporized. In one ormore embodiments, the hydrocarbon feed can be at least about 70% vol toabout 100% vol; about 80% vol to about 100% vol; or about 90% vol toabout 100% vol vaporized. The hydrocarbon feed can be a minimum of 80%wt vaporized; 85% wt vaporized; 90% wt vaporized; 95% wt vaporized; orabout 99% wt vaporized prior to introduction to the riser 605. Withinthe riser 605, the pressure and temperature can be adjusted eithermanually or automatically to compensate for variations in hydrocarbonfeed composition and to maximize the yield of preferred hydrocarbonsobtained by cracking the hydrocarbon feed in the presence of the one ormore doped catalysts.

In one or more embodiments, the steam introduced via line 630 to the oneor more risers 605 can be saturated. The pressure of the saturated steamcan be a minimum of about 1,000 kPa, about 2,000 kPa, about 4,000 kPa,or about 6,000 kPa. In one or more embodiments, the pressure of thesaturated steam can range from about 100 kPa to about 8,300 kPa; about100 kPa to about 4,000 kPa; or about 100 kPa to about 2,000 kPa.

In one or more embodiments, the steam introduced via line 630 to the oneor more risers 605 can be superheated. In one or more embodiments, wheresuperheated steam is used, the pressure of the superheated steam can bea minimum of about 1,000 kPa, about 2,000 kPa, about 4,000 kPa, or about6,000 kPa. In one or more embodiments, the pressure of the superheatedsteam can range from about 100 kPa to about 8,300 kPa; about 100 kPa toabout 4,000 kPa; or about 100 kPa to about 2,000 kPa. In one or moreembodiments, the temperature of the superheated steam can be a minimumof about 200° C., about 230° C., about 260° C., or about 290° C.

The steam can be introduced via line 630 to the riser 605 at a rateproportionate to the hydrocarbon feed rate via line 635. Thesteam-to-hydrocarbon feed weight ratio can range from about 1:20 toabout 50:1; from about 1:20 to about 20:1; or from about 1:10 to about20:1.

The first product in line 650 can include from about 5% wt to about 30%wt C₂; about 5% wt to about 60% wt C₃; about 5% wt to about 40% wt C₄;about 5% wt to about 50% wt C₅, and heavier hydrocarbons. Thetemperature of the first product in line 650 can range from about 425°C. to about 815° C.; about 450° C. to about 760° C.; or about 480° C. toabout 730° C.

Although not shown, the separation zone 615 can be disposed above (notshown) the riser 605. In one or more embodiments, the separation zone615 can include a separation zone discharge (not shown), which canprovide fluid communication between the separation zone 615 andregenerator 140. The separation zone discharge 615 can include one ormore valves to manually or automatically adjust or control the flow ofspent catalyst to the regenerator 140 based on parameters derived fromprocess temperatures, pressures, flows, and/or other process conditions.

PROPHETIC EXAMPLES

Embodiments of the present invention can be further described with thefollowing simulated processes. The following simulated process resultsare based on a mathematical model simulating both combustion kineticsand fluid bed hydrodynamics. Tables 1-6 illustrate a base case and abase case modified according to embodiments discussed and describedherein. Table 1 shows simulated process results for a base case A inwhich a distributor 150 is positioned within the lower portion or firstzone 146 of the dense phase catalyst zone 145 (note that theconfiguration for base case A is not depicted in FIGS. 1-6). Therefore,the spent catalyst and carrier fluid mixture for base case A isintroduced to the lower zone 146. Modified case A, in contrast, placesthe distributor 150 above the surface 149 of the dense phase catalystzone 145, thereby introducing the spent catalyst/carrier fluid mixtureabove the surface 149 of the dense phase catalyst zone 145 and into theupper or transitional zone 148, as discussed and described above withreference to FIG. 1. For Tables 1-3 the carrier fluid introduced vialine 129 is air. No CO promoter is used in either the base case A or themodified case A. It should be noted that for every case, i.e. base casesA-C and modified cases A-C shown in Tables 1-3, the coke burning rateremains the same with 5,350 kg/hr of coke burned.

TABLE 1 Base Modified Case A Case A Carrier Fluid Introduced via Line129 Air Air Spent Catalyst Inlet Temperature, ° C. 537 537 RegeneratedCatalyst Outlet Temperature, ° C. 712 706 Carbon Content (wt %) onRegenerated Catalyst 0.03 0.05 Carbon Content (wt %) on Spent Catalyst0.78 0.80 Coke Burning Rate, kg/hr 5348 5348 Total Catalyst Inventory,kg 73.8 80.8 Lower Temperature, ° C. 702 706 Zone 146 of Density, kg/m³410 455 Fluidized Superficial Gas Velocity, m/s 0.82 0.53 Catalyst Bedwt % Carbon in Catalyst Bed 0.06 0.05 Conditions CO % mol leaving FirstZone 1.28 1.02 NOx ppm leaving First Zone 66.5 78.4 O₂ % mol leavingFirst Zone 8.94 6.58 Coke Burning Rate, kg/hr 3626 2788 CatalystInventory, tonnes 20.0 22.1 Middle Temperature, ° C. 712 697 Zone 147 ofDensity, kg/m³ 402 450 Fluidized Superficial Gas Velocity, m/s 0.89 0.56Catalyst Bed wt % Carbon in Catalyst Bed 0.03 0.09 Conditions CO % molleaving Catalyst Bed 0.65 2.04 NOx ppm leaving Second Zone 82.5 1.5 O₂ %mol leaving Second Zone 3.07 0.2 Coke Burning Rate, kg/hr 1495 1280Catalyst Inventory, tonnes 40.6 45.4 Upper Temperature, ° C. 713 641Zone 148 of Density, kg/m³ 399 150 Fluidized Superficial Gas Velocity,m/s 0.93 0.86 Catalyst Bed wt % Carbon in Catalyst Bed 0.03 0.32Conditions CO % mol leaving Third Zone 0.64 1.64 NOx ppm leaving ThirdZone 81.5 10.5 O₂ % mol leaving Third Zone 2.94 6.75 Coke Burning Rate,kg/hr 91 183 Catalyst Inventory, tonnes 1.43 1.45 Dilute Phase CarbonContent (wt %) 0.01 0.19 Zone 155 CO % mol leaving Dilute Phase 0.031.24 Zone NOx ppm leaving Dilute Phase 165 16 Zone O₂ % mol leavingDilute Phase 2.14 2.73 Zone Coke Burning Rate, kg/hr 136 1097 Cyclone165 Cyclone Inlet Temperature, ° C. 718 678 Cyclone Outlet Temperature,° C. 721 778 Cyclone Catalyst Loading, 14.0 13.3 tonnes/min Flue Gas CO% mol 0 0 Composition NOx ppm 165 16 via line 170 O₂ % mol 2.12 2.12

As shown in Table 1, base case A provides a flue gas via line 170 thatcontains 165 ppm NOx, while the modified case A provides a flue gas vialine 170 that contains 15.7 ppm. With the exception of the lower zone146 the amount of NOx within the regenerator 140 for the modified case Ais less than for the base case A. For example, the NOx concentration inthe middle zone 147 in the modified case A is 1.5 ppm NOx versus 82.5ppm NOx for the base case A and for the NOx concentration in the upperzone 148 in the modified case A is 10.5 ppm NOx versus 81.5 ppm NOx forthe base case A.

As shown in Table 1, the CO and carbon present within the regenerator140 in the middle zone 147, upper zone 148, and dilute phase catalystzone 155 increased for the modified case A. The increase in CO andcarbon within these zones increases the amount of NOx that can beconverted to N₂ within the regenerator 140, thereby providing a flue gasvia line 170 having a reduced NOx content. As illustrated in Table 1,the flue gas via line 170 for the modified case A contains about 90.5%less NOx than in base case A (165 ppm NOx for the base case A comparedto 15.7 ppm NOx for the modified case A).

As shown in Table 1, the temperature of the flue gas at the cyclone 165inlet for base case A is 718° C., while the temperature of the flue gasat the cyclone 165 outlet is 721° C., which is only a 3° C. temperaturedifference. However, for the modified case A the temperature of the fluegas at the cyclone 165 inlet is 678° C. and the temperature of the fluegas at the cyclone 165 outlet is 778° C., a 100° C. difference. Thisincreased temperature difference for the modified case A is attributedto afterburning of the CO within the cyclone 165, as discussed anddescribed above with reference to FIG. 1. The increase in temperaturewithin the cyclones 165 and the flue gas via line 170 remains withinoperationally acceptable ranges, while providing a flue gas havingreduced NOx concentrations.

Table 2 shows simulated process results for a base case B and a modifiedcase B, which are both the same as discussed above with reference toTable 1, except a medium activity level CO promoter has been introducedto the catalyst regeneration system for both the base case B and themodified case B, as discussed and described above with reference to FIG.2. For these simulated results the medium activity level CO promoter wasplatinum at a concentration of 0.7 ppm in the catalyst regenerationsystem.

TABLE 2 Base Modified Case B Case B Carrier Fluid Introduced via Line129 Air Air Spent Catalyst Inlet Temperature, ° C. 537 537 RegeneratedCatalyst Outlet Temperature, ° C. 712 707 Carbon Content (wt %) onRegenerated Catalyst 0.03 0.05 Carbon Content (wt %) on Spent Catalyst0.78 0.8 Coke Burning Rate, kg/hr 5348 5348 Total Catalyst Inventory,tonnes 73.8 80.7 Lower Temperature, ° C. 703 707 Zone 146 of Density,kg/m³ 408 455 Fluidized Superficial Gas Velocity, m/s 0.82 0.53 CatalystBed wt % Carbon in Catalyst Bed 0.06 0.05 Conditions CO % mol leavingFirst Zone 0.91 0.82 NOx ppm leaving First Zone 91.1 85.2 O₂ % molleaving First Zone 8.73 5.26 Coke Burning Rate, kg/hr 3399 2992 CatalystInventory, tonnes 20 22.1 Middle Temperature, ° C. 712 697 Zone 147 ofDensity, kg/m³ 402 449 Fluidized Superficial Gas Velocity, m/s 0.89 0.56Catalyst Bed wt % Carbon in Catalyst Bed 0.03 0.1 Conditions CO % molleaving Catalyst Bed 0.49 1.56 NOx ppm leaving Second Zone 107 1.1 O₂ %mol leaving Second Zone 2.99 0.1 Coke Burning Rate, kg/hr 1768 1042Catalyst Inventory, tonnes 40.6 45.3 Upper Temperature, ° C. 713 642Zone 148 of Density, kg/m³ 397 150 Fluidized Superficial Gas Velocity,m/s 0.93 0.86 Catalyst Bed wt % Carbon in Catalyst Bed 0.03 0.33Conditions CO % mol leaving Third Zone 0.48 1.31 NOx ppm leaving ThirdZone 106 12.9 O₂ % mol leaving Third Zone 2.86 6.67 Coke Burning Rate,kg/hr 45 181 Catalyst Inventory, tonnes 1.43 1.45 Dilute Phase CarbonContent (wt %) 0.015 0.197 Zone 155 CO % mol leaving Dilute Phase 0.031.05 Zone NOx ppm leaving Dilute Phase 185 18 Zone O₂ % mol leavingDilute Phase 2.14 2.64 Zone Coke Burning Rate, kg/hr 136 1133 Cyclone165 Cyclone Inlet Temperature, ° C. 717 678 Cyclone Outlet Temperature,° C. 719 762 Cyclone Catalyst Loading, 14.0 13.3 tonnes/min Flue Gas CO% mol 0 0 Composition NOx ppm 186 18 via line 170 O₂ % mol 2.12 2.12

Table 2 shows similar results as Table 1, however the NOx concentrationin the flue gas via line 170 is slightly higher for both the base case Band the modified case B, which is 186 ppm NOx and 17.9 ppm NOx,respectively. This result is expected because the presence of the mediumactivity CO promoter results in more complete combustion of the CO and,therefore, less CO is present within the regenerator that can react withthe NOx to provide CO₂ and N₂. However, the increase in NOx for themodified case B is only slight, i.e. 2.2 ppm NOx, over the modified basecase A.

The use of the medium activity level CO promoter also results in less COafterburning for the modified case B than in the modified case A. Thisreduction in CO afterburning can be seen by the reduction in thetemperature rise of the flue gas between the inlet and outlet of thecyclone 165. Specifically, the flue gas enters the cyclone 165 at atemperature of 678° C. and exits the cyclone 165 at a temperature of762° C. Therefore, the modified case B provides a flue gas via line 170having a temperature of 16° C. less than the flue gas provided inmodified case A.

Table 3 shows simulated process results for a base case C and a modifiedcase C, which are both the same as in Table 1, except a high activity COpromoter has been introduced to the catalyst regeneration system forboth the base case C and the modified case C, as discussed and describedabove with reference to FIG. 2. For these simulated results the highactivity level CO promoter was platinum at a concentration of 1.5 ppm inthe catalyst regeneration system.

TABLE 3 Base Modified Case C Case C Carrier fluid introduced via line129 Air Air Catalyst Regeneration Temperature, ° C. 712 711 CarbonContent (wt %) on Regenerated Catalyst 0.03 0.07 Carbon Content (wt %)on Spent Catalyst 0.78 0.81 Coke Burning Rate, kg/hr 5348 5348 TotalCatalyst Inventory, tonnes 73.8 80.7 First Temperature, ° C. 703 711Zone 146 of Density, kg/m³ 408 455 Fluidized Superficial Gas Velocity,m/s 0.82 0.54 Catalyst Bed wt % Carbon in Catalyst Bed 0.06 0.07Conditions CO % mol leaving First Zone 0.43 0.45 NOx ppm leaving FirstZone 184 117 O₂ % mol leaving First Zone 8.46 3.56 Coke Burning Rate,kg/hr 3399 3263 Catalyst Inventory, tonnes 20 22.1 Second Temperature, °C. 712 699 Zone 147 of Density, kg/m³ 402 449 Fluidized Superficial GasVelocity, m/s 0.88 0.57 Catalyst Bed wt % Carbon in Catalyst Bed 0.030.12 Conditions CO % mol leaving Catalyst Bed 0.25 0.81 NOx ppm leavingSecond Zone 204 0.8 O₂ % mol leaving Second Zone 2.87 0.03 Coke BurningRate, kg/hr 1768 680 Catalyst Inventory, tonnes 40.6 45.3 ThirdTemperature, ° C. 713 643 Zone 148 of Density, kg/m³ 397 150 FluidizedSuperficial Gas Velocity, m/s 0.93 0.86 Catalyst Bed wt % Carbon inCatalyst Bed 0.03 0.34 Conditions CO % mol leaving Third Zone 0.24 0.79NOx ppm leaving Third Zone 199 21 O₂ % mol leaving Third Zone 2.75 6.58Coke Burning Rate, kg/hr 45 227 Catalyst Inventory, tonnes 1.43 1.45Dilute Phase Carbon Content (wt %) 0.02 0.2 Zone 155 CO % mol leavingDilute Phase 0.31 1.05 Zone NOx ppm leaving Dilute Phase 263 27 Zone O₂% mol leaving Dilute Phase 2.12 2.44 Zone Coke Burning Rate, kg/hr 1361178 Cyclone 165 Cyclone Inlet Temperature, ° C. 715 681 Cyclone OutletTemperature, ° C. 718 733 Cyclone Catalyst Loading, 14.0 13.3 tonnes/minFlue Gas NOx ppm 263 27 Composition CO % mol 0 0 via line 170 O₂ % mol2.12 2.12

Table 3 shows similar results as Tables 1 and 2, however the NOxconcentration in the flue gas via line 170 is higher for both the basecase C and the modified case C, which is 263 ppm NOx and 26.8 ppm NOx,respectively. Again this result is expected because the presence of thehigh activity CO promoter results in a further combustion of the CO anda further reduction in CO afterburning than in the base cases A and Band the modified cases A and B. The further reduction of CO afterburningcan be seen by the further decrease in the temperature rise of the fluegas between inlet and outlet of the cyclone 165. Specifically, the fluegas enters the cyclone 165 at a temperature of 681° C. and exits thecyclone 165 at a temperature of 733° C. Therefore, the modified case Cprovides a flue gas via line 170 having a temperature 45° C. less thanthe flue gas provided in modified case A and 29° C. less than the fluegas provided in modified case B.

The increase in NOx in the flue gas for the modified case C stillresults in a flue gas in line 170 having a reduced NOx concentrationversus the base case C (26.8 ppm NOx versus 263 ppm NOx). Furthermore,the increase in NOx in the flue gas for the modified case C stillresults in a flue gas in line 170 having a reduced NOx concentrationversus the base case A which did not use a CO promoter (26.8 ppm NOxversus 165 ppm NOx).

Table 4 shows various operating and other simulation conditions used forthe determination of the simulated results.

TABLE 4 Base Modified Cases A-C Cases A-C Geometries Bed Level, m 6.496.49 Bed Diameter of Bottom 5.49 5.49 Section, m Top Section Heights, m8.96 8.96 Top Section Diameter, m 5.49 5.49 Conditions CatalystCirculation Rate, kg/min 11200 11200 Spent Catalyst Temperature, ° C.538 538 Regenerator Top Pressure, kPa 177 177 Spent Catalyst Lift Gas 00 (not air), m³/min Total Combustion Air, m³/min 1050 1050 CombustionAir to Air 682 682 Grids, m³/min Combustion Air to Spent 368 368Catalyst Line, m³/min Air from Air Blower to 0 0.35 Upper Zone 148 Airfrom Air Blower to 0 0 Middle Zone 147 Air from Air Blower to 1 0.65Lower Zone 146 Catalyst Flow from 0 1 Reactor to Upper Zone 148 CatalystFlow from 0 0 Reactor to Middle Zone 147 Catalyst Flow from 1 0 Reactorto Lower Zone 146 Catalyst Cooler Duty, kJ/hr 0 0 Carbon on Spent -Regenerated 0.75 0.75 Catalyst, wt % cat H₂ in Coke Burned, wt % 6 6Delta Nitrogen, wt ppm 112 112 Tuning Catalytic CO Burn Factor 0.5-30.5-3 Parameters (CO promoter)

The information in the rows labeled “Geometries” describe the size ofthe regenerator and the depth (bed level) of the dense phase catalystbed contained within the regenerator. The top section height refers tothe vertical height of the dilute phase catalyst zone within theregeneration vessel. The spent catalyst temperature is the temperatureof the coked catalyst particles when introduced to the regenerationvessel. The regenerator top pressure is the pressure of the vapor in theuppermost region of the regenerator. Spent catalyst lift gas refers tothe rate of gas (other than air) that is used to transport spentcatalyst into the regenerator. Combustion air refers to the total amountof air injected into the regenerator. The relative flow rates of air andcatalyst into the different zones of the regenerator are also shown inTable 4. None of these cases include any heat removal from theregenerator via steam generation using a catalyst cooler or otherdevice. The carbon on spent catalyst—regenerated catalyst refers to thechange in concentration of carbon on the catalyst as the catalyst passesthrough the regeneration process. Hydrogen in coke is the percentage ofhydrogen in the coke burned in the regenerator. Delta nitrogen refers tothe change in concentration of nitrogen on the catalyst as the catalystpasses through the regeneration process.

Table 5 shows results for a base case D and modified case D that aresimilar to Table 1, except the carrier fluid has been changed to anoxygen-lean carrier fluid, namely a mixture of steam and combustion gas.Specifically, Table 5 shows simulated process results for a base case Din which the distributor 150 is positioned within the lower zone 146 ofa dense phase catalyst zone 145 (note that the configuration for basecase D is not depicted in FIGS. 1-6). As such, the spent catalyst andcarrier fluid mixture is introduced to the first zone 146. Modified caseD in contrast places the distributor 150 above the surface 149 of thefluidized catalyst bed 145, thereby introducing the spentcatalyst/carrier fluid mixture above the surface 149 of the fluidizedcatalyst bed 145, as discussed and described above with reference toFIG. 1. For the simulated results shown in Table 5, a high activitylevel CO promoter was used. The particular CO promoter was platinum at aconcentration of 1.5 ppm in the regeneration system. The coke burningrate remains the same, which is 5,350 kg/hr. The cyclone catalystloading or entrainment rate within the dilute phase catalyst bed 155 was14.0 kg/min for the base case D and 22.4 tonnes/min for the modifiedcase D.

TABLE 5 Base Modified Case D Case D Carrier fluid introduced via line129 Combus- Combus- tion Gas tion Gas and Steam and Steam CatalystRegeneration Temperature, ° C. 712 711 Carbon Content (wt %) onRegenerated Catalyst 0.03 0.01 Carbon Content (wt %) on Spent Catalyst0.78 0.76 Coke Burning Rate, kg/hr 5350 5350 Total Catalyst Inventory,tonnes 73.8 77.1 First Temperature, ° C. 703 711 Zone 146 of Density,kg/m³ 408 408 Fluidized Superficial Gas Velocity, m/s 0.82 0.83 CatalystBed wt % Carbon in Catalyst Bed 0.06 0.01 Conditions CO % mol leavingFirst Zone 0.43 0.06 NOx ppm leaving First Zone 184 434 O₂ % mol leavingFirst Zone 8.46 18.05 Coke Burning Rate, kg/hr 3399 861 CatalystInventory, tonnes 20 20 Second Temperature, ° C. 712 713 Zone 147 ofDensity, kg/m³ 402 405 Fluidized Superficial Gas Velocity, m/s 0.88 0.87Catalyst Bed wt % Carbon in Catalyst Bed 0.03 0.02 Conditions CO % molleaving Catalyst Bed 0.25 0.17 NOx ppm leaving Second Zone 204 471 O₂ %mol leaving Second Zone 2.87 8.65 Coke Burning Rate, kg/hr 1768 2674Catalyst Inventory, tonnes 40.6 40.9 Third Temperature, ° C. 713 659Zone 148 of Density, kg/m³ 397 150 Fluidized Superficial Gas Velocity,m/s 0.93 0.87 Catalyst Bed wt % Carbon in Catalyst Bed 0.03 0.26Conditions CO % mol leaving Third Zone 0.24 0.58 NOx ppm leaving ThirdZone 199 107 O₂ % mol leaving Third Zone 2.75 7.81 Coke Burning Rate,kg/hr 45 272 Catalyst Inventory, tonnes 1.43 1.45 Dilute Phase CarbonContent (wt %) 0.02 0.15 Zone 155 CO % mol leaving Dilute Phase 0 0.46Zone NOx ppm leaving Dilute Phase 263 41 Zone O₂ % mol leaving DilutePhase 2.14 2.35 Zone Coke Burning Rate, kg/hr 136 1541 Cyclone 165Cyclone Inlet Temperature, ° C. 715 690 Cyclone Outlet Temperature, ° C.718 727 Cyclone Catalyst Loading, 14.0 22.4 tonnes/min Flue Gas NOx ppm263 41 Composition CO % mol 0 0 via line 170 O₂ % mol 2.12 2.12

As shown in Table 5, base case D provides a flue gas via line 170 thatcontains 265 ppm NOx, while the modified case D provides a flue gas vialine 170 that contains only 41 ppm. The CO and carbon present within theregenerator 140 in the upper zone 148 and dilute phase catalyst zone 155increased for the modified case D over the base case D. The increase inCO and carbon within these zones increases the amount of NOx that can beconverted to N₂ within the regenerator 140, thereby providing a flue gasvia line 170 having a substantially reduced NOx content for the modifiedcase D versus the base case D. As illustrated in Table 5, the flue gasvia line 170 for the modified case D contains about 84.4% less NOx thanin base case D (263 ppm NOx for the base case D compared to only 41 ppmNOx for the modified case D).

As shown in Table 5, the temperature of the flue gas at the cyclone 165inlet for base case D is 715° C., while the temperature of the flue gasat the cyclone 165 outlet is 718° C., which is only a 3° C. temperaturedifference. However, for the modified case D the temperature of the fluegas at the cyclone 165 inlet is 690° C. and the temperature of the fluegas at the cyclone 165 outlet is 727° C., a 37° C. difference. Thisincreased temperature difference for the modified case D is attributedto afterburning of the CO within the cyclone 165, as discussed anddescribed above with reference to FIG. 1. The increase in temperaturewithin the cyclones 165 and the flue gas via line 170 remains withinoperationally acceptable ranges, while providing a flue gas havingreduced NOx concentrations.

Similar to Table 4, Table 6 shows various operating and other simulationconditions used for the determination of the simulated results.

TABLE 6 Base Modified Case D Case D Geometries Bed Level, m 6.49 6.49Bed Diameter of Bottom 5.49 5.49 Section, m Top Section Heights, m 8.968.96 Top Section Diameter, m 5.49 5.49 Conditions Catalyst CirculationRate, kg/min 11200 11200 Spent Catalyst Temperature, ° C. 538 538Regenerator Top Pressure, kPa 177 177 Spent Catalyst Lift Gas 0 315 (notair), m³/min Total Combustion Air, m³/min 1050 1050 Combustion Air fromAir 682 1050 Blower, m³/min Combustion Air to Spent 368 0 CatalystCarrier Line, m³/min Air from Air Blower to 0 0 Upper Zone 148 Air fromAir Blower to 0 0 Middle Zone 147 Air from Air Blower to 1 1 Lower Zone146 Catalyst Flow from 0 1 Reactor to Upper Zone 148 Catalyst Flow from0 0 Reactor to Middle Zone 147 Catalyst Flow from 1 0 Reactor to LowerZone 146 Catalyst Cooler Duty, kJ/hr 0 0 Carbon on spent - Regenerated0.75 0.75 Catalyst, wt % cat H₂ in Coke Burned, wt % 6 6 Delta Nitrogen,wt ppm 112 112 Tuning Catalytic CO Burn Factor 3.0 3.0 Parameters (COpromoter)

Embodiments of the present invention further relate to any one or moreof the following paragraphs:

1. A method for regenerating a spent catalyst, comprising: mixing aspent catalyst with a carrier fluid to provide a mixture, wherein thespent catalyst includes carbon deposited on at least a portion thereof,and wherein the carrier fluid comprises an oxygen containing gas;introducing the mixture to or above an upper surface of a dense phasecatalyst zone disposed within a regenerator; introducing a gas to alower zone of the dense phase catalyst zone; and combusting at least aportion of the carbon deposited on the catalyst to provide a flue gas,heat, and a regenerated catalyst.

2. The method according to paragraph 1, wherein the carrier fluidcomprises from about 10% to about 90% of the total amount of gasintroduced to the regenerator, and wherein the carrier fluid comprisesfrom 0% to about 90% of the total amount of oxygen introduced to theregenerator.

3. The method according to paragraphs 1 or 2, wherein the carrier fluidcomprises from about 20% to about 50% of the total amount of gasintroduced to the regenerator, and wherein the carrier fluid comprisesfrom about 0% to about 50% of the total amount of oxygen introduced tothe regenerator.

4. The method according to paragraph 3, further comprising introducingan oxygen containing gas to the regenerator above the surface of thedense phase catalyst zone.

5. The method according to any of paragraphs 1 to 4, wherein the fluegas comprises less than about 150 ppm nitrogen oxides.

6. The method according to any of paragraphs 1 to 5, wherein introducingthe mixture to the upper surface of the dense phase catalyst zonefurther comprises introducing at least a portion of the mixture to anupper portion of the dense phase catalyst zone disposed below thesurface of the dense phase catalyst zone, a dilute phase catalyst zonedisposed above the dense phase catalyst zone, or both.

7. The method according to any of paragraphs 1 to 6, wherein the gascomprises an oxygen-lean gas, air, or oxygen-rich gas.

8. The method according to paragraph 7, wherein the ratio of the oxygenintroduced with the carrier fluid to the oxygen introduced with the gasranges from about 1:1 to about 1:3.

9. The method according to any of paragraphs 1 to 8, wherein the carbondeposited on the spent catalyst ranges from about 0.7% wt to about 1.3%wt.

10. The method according to any of paragraphs 1 to 9, further comprisingintroducing a carbon monoxide combustion promoter to the regenerator.

11. The method according to paragraph 10, wherein the carbon monoxidecombustion promoter comprises platinum at a concentration of rangingfrom about 0.01 ppm to about 3 ppm.

12. A method for regenerating a spent catalyst, comprising: mixing aspent catalyst with a carrier fluid to provide a mixture, wherein thespent catalyst includes carbon deposited on at least a portion thereof;introducing the mixture to a regenerator, wherein the regeneratorcomprises a dense phase catalyst zone and a dilute phase catalyst zonedisposed above the dense phase catalyst zone; and wherein the mixture isintroduced to or above an upper surface of the dense phase catalystzone; introducing a gas to a lower portion of the dense phase catalystzone; combusting at least a portion of the carbon deposited on the spentcatalyst to provide a flue gas, heat, and a regenerated catalyst;introducing at least a portion of the regenerated catalyst to afluidized catalytic cracker; and recovering the flue gas from theregenerator, wherein the flue gas comprises less than about 150 ppmnitrogen oxides.

13. The method according to paragraph 12, wherein introducing themixture to or above the upper surface of the dense phase catalyst zonefurther comprises introducing at least a portion of the mixture to anupper portion of the dense phase catalyst zone disposed below the uppersurface of the dense phase catalyst zone, the dilute phase catalystzone, or both.

14. The method according to paragraphs 12 or 13, wherein the carrierfluid comprises from about 10% to about 90% of a total amount of gasintroduced to the regenerator, and wherein the carrier fluid comprisesfrom about 0% to about 90% of the total amount of oxygen introduced tothe regenerator.

15. The method of according to any of paragraphs 12 to 14, wherein thecarrier fluid comprises less than about 50% of a total amount of gasintroduced to the regenerator, and wherein the carrier fluid comprisesless than about 50% of the total amount of oxygen introduced to theregenerator.

16. The method of according to any of paragraphs 12 to 15, furthercomprising introducing air, an oxygen-rich gas, or a combination thereofto the dilute phase catalyst zone.

17. The method according to any of paragraphs 12 to 16, furthercomprising introducing a carbon monoxide combustion promoter to theregenerator.

18. The method of according to paragraph 17, wherein the concentrationof the carbon monoxide combustion promoter ranges from about 0.3 ppm toabout 2 ppm

19. A method for regenerating a spent catalyst, comprising: mixing aspent catalyst with a carrier fluid to provide a mixture, wherein thespent catalyst includes carbon deposited on at least a portion thereof;introducing the mixture to a lower zone, an intermediate zone, an upperzone, or any combination thereof of a dense phase catalyst zone disposedbelow a dilute phase catalyst zone in a regenerator; introducing a gasto the lower zone; introducing an oxygen containing gas to the dilutephase catalyst zone; combusting at least a portion of the carbondeposited on the catalyst to provide a flue gas, heat, and a regeneratedcatalyst.

20. The method according to paragraph 19, wherein the carrier fluidcomprises a gas containing less than about 5% vol oxygen.

21. The method according to paragraphs 19 or 20, wherein the oxygencontaining gas comprises a gas mixture containing at least 10% voloxygen.

22. The method according to any of paragraphs 19 to 21, wherein the gascomprises air, an oxygen-lean gas, or an oxygen-rich gas.

23. The method according to any of paragraphs 19 to 22, wherein thecarbon deposited on the spent catalyst ranges from about 0.7% wt toabout 1.3% wt.

24. The method according to any of paragraphs 19 to 23, furthercomprising introducing a carbon monoxide combustion promoter to theregenerator.

25. The method according to paragraph 24, wherein the concentration ofthe carbon monoxide combustion promoter ranges from about 0.3 ppm toabout 2 ppm.

Certain embodiments and features have been described using a set ofnumerical upper limits and a set of numerical lower limits. It should beappreciated that ranges from any lower limit to any upper limit arecontemplated unless otherwise indicated. Certain lower limits, upperlimits and ranges appear in one or more claims below. All numericalvalues are “about” or “approximately” the indicated value, and take intoaccount experimental error and variations that would be expected by aperson having ordinary skill in the art.

Various terms have been defined above. To the extent a term used in aclaim is not defined above, it should be given the broadest definitionpersons in the pertinent art have given that term as reflected in atleast one printed publication or issued patent. Furthermore, allpatents, test procedures, and other documents cited in this applicationare fully incorporated by reference to the extent such disclosure is notinconsistent with this application and for all jurisdictions in whichsuch incorporation is permitted.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. A method for regenerating a spent catalyst,comprising: mixing a spent catalyst with a carrier fluid to provide amixture, wherein the spent catalyst includes carbon deposited on atleast a portion thereof, and wherein the carrier fluid comprises anoxygen containing gas; introducing the mixture to a dilute phasecatalyst zone disposed within a regenerator; distributing the mixture ofthe dilute phase catalyst zone onto an upper surface of a dense phasecatalyst zone disposed within the regenerator; introducing a gas to alower zone of the dense phase catalyst zone; and combusting at least aportion of the carbon deposited on the catalyst to provide a flue gas,heat, and a regenerated catalyst.
 2. The method of claim 1, wherein thecarrier fluid comprises from about 10% to about 90% of the total amountof gas introduced to the regenerator, and wherein the carrier fluidcomprises from 0.5% to about 90% of the total amount of oxygenintroduced to the regenerator.
 3. The method of claim 1, wherein thecarrier fluid comprises from about 20% to about 50% of the total amountof gas introduced to the regenerator, and wherein the carrier fluidcomprises from about 0.5% to about 50% of the total amount of oxygenintroduced to the regenerator.
 4. The method of claim 3, furthercomprising introducing an oxygen containing gas to the regenerator abovethe upper surface of the dense phase catalyst zone.
 5. The method ofclaim 1, wherein the flue gas comprises less than about 150 ppm nitrogenoxides.
 6. The method of claim 1, further comprising distributing themixture above the upper surface of the dense phase catalyst zone.
 7. Themethod of claim 1, wherein the gas comprises an oxygen-lean gas, air, oroxygen-rich gas.
 8. The method of claim 7, wherein the ratio of theoxygen introduced with the carrier fluid to the oxygen introduced withthe gas ranges from about 1:1 to about 1:3.
 9. The method of claim 1,wherein the carbon deposited on the spent catalyst ranges from about0.7% wt to about 1.3% wt.
 10. The method of claim 1, further comprisingintroducing a carbon monoxide combustion promoter to the regenerator.11. The method of claim 10, wherein the carbon monoxide combustionpromoter comprises platinum at a concentration of ranging from about0.01 ppm to about 3 ppm.
 12. A method for regenerating a spent catalyst,comprising: mixing a spent catalyst with a carrier fluid to provide amixture, wherein the spent catalyst includes carbon deposited on atleast a portion thereof; introducing the mixture to a dilute phasecatalyst zone disposed above a dense phase catalyst zone in aregenerator; distributing the mixture of the dilute phase catalyst zoneonto an upper surface of the dense phase catalyst zone; introducing agas to a lower portion of the dense phase catalyst zone; combusting atleast a portion of the carbon deposited on the spent catalyst to providea flue gas, heat, and a regenerated catalyst; introducing at least aportion of the regenerated catalyst to a fluidized catalytic cracker;and recovering the flue gas from the regenerator, wherein the flue gascomprises less than about 150 ppm nitrogen oxides.
 13. The method ofclaim 12, further comprising distributing the mixture above the uppersurface of the dense phase catalyst zone.
 14. The method of claim 12,wherein the carrier fluid comprises from about 10% to about 90% of atotal amount of gas introduced to the regenerator, and wherein thecarrier fluid comprises from about 0% to about 90% of the total amountof oxygen introduced to the regenerator.
 15. The method of claim 12,wherein the carrier fluid comprises less than about 50% of a totalamount of gas introduced to the regenerator, and wherein the carrierfluid comprises less than about 50% of the total amount of oxygenintroduced to the regenerator.
 16. The method of claim 12, furthercomprising introducing air, an oxygen-rich gas, or a combination thereofto the dilute phase catalyst zone.
 17. The method of claim 12, furthercomprising introducing a carbon monoxide combustion promoter to theregenerator.
 18. The method of claim 17, wherein the concentration ofthe carbon monoxide combustion promoter ranges from about 0.3 ppm toabout 2 ppm.
 19. A method for regenerating a spent catalyst, comprising:mixing a spent catalyst with a carrier fluid to provide a dilute phasemixture, wherein the spent catalyst includes carbon deposited on atleast a portion thereof; introducing the dilute phase mixture to adilute phase catalyst zone disposed above a dense phase catalyst zone ina regenerator; distributing the dilute phase mixture of the dilute phasecatalyst zone onto an upper surface of the dense phase catalyst zone;introducing a gas to the lower zone; introducing an oxygen containinggas to the dilute phase catalyst zone; and combusting at least a portionof the carbon deposited on the catalyst to provide a flue gas, heat, anda regenerated catalyst.
 20. The method of claim 19, wherein the carrierfluid comprises a gas containing less than about 5% vol oxygen.
 21. Themethod of claim 19, wherein the oxygen containing gas comprises a gasmixture containing at least 10% vol oxygen.
 22. The method of claim 19,wherein the gas comprises air, an oxygen-lean gas, or an oxygen-richgas.
 23. The method of claim 19, wherein the carbon deposited on thespent catalyst ranges from about 0.7% wt to about 1.3% wt.
 24. Themethod of claim 19, further comprising introducing a carbon monoxidecombustion promoter to the regenerator.
 25. The method of claim 24,wherein the concentration of the carbon monoxide combustion promoterranges from about 0.3 ppm to about 2 ppm.
 26. The method of claim 1,wherein the total amount of gas introduced to the regenerator is fromabout 80% to about 115% of the stoichiometric oxygen required to oxidizeall of the coke and carbon monoxide within the regenerator.
 27. Themethod of claim 1, wherein the flue gas comprises less than about 40 ppmnitrogen oxides.
 28. The method of claim 1, wherein the flue gascomprises less than about 0.1 mol% carbon monoxide.
 29. The method ofclaim 1, further comprising distributing the mixture above the uppersurface of the dense phase catalyst zone.
 30. The method of claim 19,wherein the dilute phase catalyst zone has a catalyst concentration fromabout 50 kg/m³ to about 160 kg/m³.
 31. The method of claim 1, whereinthe carrier fluid comprises from about 10% to about 90% of the totalamount of gas introduced to the regenerator, and wherein the carrierfluid comprises from 40 to about 90% of the total amount of oxygenintroduced to the regenerator.
 32. The method of claim 12, wherein thecarrier fluid comprises from about 10% to about 90% of the total amountof gas introduced to the regenerator, and wherein the carrier fluidcomprises from 60% to about 90% of the total amount of oxygen introducedto the regenerator.
 33. The method of claim 19, wherein the carrierfluid comprises from 10% to about 60% of the total amount of oxygenintroduced to the regenerator.
 34. The method of claim 19, wherein thedilute phase mixture comprises a spent catalyst concentration of lessthan 175 kg/m³.